A steering mechanism known as an Ackerman-Jeantaud steering mechanism includes a steering link mechanism connecting together right and left vehicle wheels (an assembly including a tire, a rim, a hub, an in-wheel motor, etc. is hereinafter referred to as “vehicle wheel” or simply “wheel”), and used to steer the vehicle wheels. This steering mechanism includes tie rods and knuckle arms such that while the vehicle is turning, the right and left wheels move around the same center point.
Such steering mechanisms include one disclosed in the below-identified Patent document 1. This steering mechanism includes at least one steering linkage mechanism provided for the front right and front left wheels or the rear right and rear left wheels, and includes tie rods and knuckle arms. This steering mechanism further includes an actuator capable of changing the lengths of the tie rods, the distance between the right and left tie rods, or the angle formed between each wheel and the knuckle arm, whereby the vehicle can smoothly travel in all of the normal travel mode, a parallel travel mode and a pivot turn mode.
The below-identified Patent document 2 discloses a steering mechanism including steering shafts disposed, respectively, between the front right and front left wheels and between the rear right and rear left wheels so as to be rotatable about their own axes. Each steering shaft comprises right and left separate portions between which is disposed a normal and reverse rotation switching means for switching the rotational direction of the steering shaft. The normal and reverse rotation switching means allows 90-degree steering, lateral movement of the vehicle, etc.
The below-identified Patent document 3 discloses a four-wheel steering vehicle including an actuator actuated when the front wheels are steered such that the rear wheels are steered. The below-identified Patent document 4 discloses a steering mechanism capable of performing toe adjustment of right and left wheels by moving a rack housing connecting together the right and left wheels in the fore-and-aft direction, thereby improving travel stability.
The below-identified Patent document 5 discloses a steering mechanism including two rack bars movable to right and left independently of each other, and connected, respectively, to right and left wheels through tie rods. This steering mechanism further includes a synchronizing gear box in which is retained a synchronizing gear which allows the rack bars to move in opposite directions relative to the synchronizing gear box. The steering mechanism further includes two pinion gears meshing with the respective rack bars, and a coupling mechanism disposed between the pinion gears and capable of selectively coupling and uncoupling rotary shafts of the pinion gears. When the coupling mechanism is coupled, the rack bars are fixed to each other such that the rack bars move in the same direction by the same distance, so that the right and left wheels can be steered in the same direction. When the coupling mechanism is uncoupled, the rack bars are moved in opposite directions to each other by the same distance, so that the right and left wheels can be steered in opposite directions to each other.